The two streams meet at a confluence. It takes many tributary streams to form a river. A river grows larger as it collects water from more tributaries. Streams usually form rivers in the higher elevations of mountains and hills. The areas of depression between hills or mountains are known as valleys.
The world's fastest production single piston engine aircraft produced in Great Britain, deployed from 1945 to 1953. Heavily Modified Sea Fury aircraft can be seen today as air racers. Heinkel He-162 562 mph. Arguably the fastest WW II jet fighter.
The SR-72 is the successor to the SR-71 Blackbird spy plane, which was the fastest plane to ever exist. Built by Lockheed Martin in the 1960s, the SR-71 could reach speeds exceeding Mach 3 (above 2,200 mph). That's over 3 times faster than the speed of sound. The recon jets went out of service in 1998. Development of the SR-72 was announced in 2013.